Time Warner Cable made it official that CEO and chairman Glenn Britt will retire at the end of the year, to be replaced in both roles by president and COO Robert Marcus effective Jan. 1. Britt will continue after that as a board member in a non-executive role, the firm said Thursday.

Britt, a 40-year-veteran of the TV industry, has been CEO at Time Warner Cable since 2001, orchestrating its separation from Time Warner seven years ago. Time Warner Cable said Thursday that its stock price has risen 360 percent since the spinoff and that during Britt's tenure, the company has increased its annual revenue from $6 billion to $21 billion.

"I love this business, but I'm ready to retire knowing Rob is ready to lead," said Britt, 64.

Marcus, 48, joined Time Warner in 1998 and moved to Time Warner Cable seven years later. He was made CFO in 2008 and COO in 2010.